Whistle characteristics of free-ranging Indo-Pacific humpback dolphins (Sousa chinensis) in Sanniang Bay, China

Abstract

Broadband recording systems were adapted to characterize the whistle characteristics of free-ranging Indo-Pacific humpback dolphins (Sousa chinensis) in Sanniang Bay, China. A total of 4630 whistles were recorded, of which 2651 with legible contours and relatively good signal-to-noise ratios were selected for statistical analysis. Of the six tonal types (i.e., flat, down, rise, convex, Ushaped, and sine), flat (N ¼ 1426; 39.45%) was the most predominant, followed by down (N ¼ 754; 23.35%) and rise (N ¼ 489; 12.34%). The whistles showed a short duration (mean 6 SD: 370.19 6 285.61 ms; range: 29-2923 ms), a broad frequency range (fundamental contour ranged from 0.52 to 33 kHz), and two harmonics (mean 6 SD: 1.90 6 2.74, with the maximum frequency of harmonics beyond 96 kHz). Whistles without gaps and stairs accounted for 76.7% and 86.4%, respectively. No significant interspecies differences in frequency parameters were observed compared with S. teuszii, which is inconsistent with morphological taxonomies but confirms phylogenetic results, thus suggesting a close relation between Chinese S. chinensis and Atlantic S. teuszii. Significant intra-and interspecific differences in the genus Sousa were also observed, indicating that animal vocalization may not be limited by genetically determined traits but could also be a function of local habitat adaptation.

Variation in the emission rate of sounds in a captive group of false killer whales Pseudorca crassidens during feedings: possible food anticipatory vocal activity?

“…A tonal, narrow band signal was considered as a whistle; a click train was defi ned as a series of distinct and rapid clicks with ICI (defi ned as the portion of the echolocation signal that returns to the dolphin before the production of another click) (Melcón et al, 2012) from 1 to 200 ms. Burst pulses were defi ned as many clicks in such a rapid succession that to human ear it was perceived as single buzz Acevedo-Gutiérrez and Stienessen, 2004;Díaz López, 2011;Wang et al, 2013 ) (Fig.1). The recordings included the entire false killer whales group and a single hydrophone was used with no concurrent video footage, which did not allow the identifi cation of the dolphin that produced the sounds.…”

“…Hz with a window and FFT size 1 024, producing a 3-dB fi lter bandwidth of 135 Hz) to count the total number of whistles and burst pulses. All whistles included in the categories "fair" (whistles with main contour distinguishable and can be ascribed to a specifi c tonal type), "good" (whistles with a very clear contour and with the beginning and ending points well defi ned), and "fi ne" (whistles with a good signal to noise ratio over 20 dB) were counted for each of the fi ve intervals (Díaz López, 2011;Wang et al, 2013). Successive contours were considered as one whistles if the gap between them was smaller than 200 ms and shorter than the duration of both whistles, with the former ending and the latter beginning section extended to form a linkage, with the ending-beginning frequency diff erence less than 3 kHz ( Bazúa-Durán and Au, 2002 ).…”

Echolocation signals of free-ranging Indo-Pacific humpback dolphins (Sousa chinensis) in Sanniang Bay, China

“…Though the sounds of the Indo-Pacific humpback dolphin have been described in a number of papers (Schultz and Corkeron, 1994;Van Parijs and Corkeron, 2001a,b;Goold and Jefferson, 2004;Nanayakkara et al, 2007;Sims et al, 2012;Lin et al, 2013;Wang et al, 2013;Kimura et al, 2014), most of these studies were performed with sounds recorded either within a 30-kHz frequency range (Schultz and Corkeron, 1994;Van Parijs and Corkeron, 2001a,b;Nanayakkara et al, 2007;Sims et al, 2012;Wang et al, 2013) or by a miniature stereo acoustic event data-logger a) Also at: University of Chinese Academy of Sciences, Beijing, 100039, People's Republic of China. b) Electronic mail: wangd@ihb.ac.cn (A-tag), which only records high-frequency phonating events and peak pressures, but not waveforms of the high-frequency sounds Kimura et al, 2014).…”

Stereotyped Whistles May Be First Evidence to Suggest the Possibility of Signature Whistles in an InjuredIndo-Pacific Humpback Dolphin (Sousa chinensis

“…Signature whistles are thought to serve widths (by approximately 0.78 kHz) compared as a cohesion call and can provide information to the Indo-Pacific humpback dolphin, while about identity, stress, social relationships, and the minimum frequency of Indo-Pacific humpcontext-related information (Janik et al, 1994, back dolphin whistles has been found to be 2006; Sayigh et al, 1995Sayigh et al, , 1999Janik & Slater, higher compared to their Atlantic cousins (Weir, 1998;Esch et al, 2009). Signature whistles are 2010; Wang et al, 2013). However, when a learned within the first year of life (Caldwell & single female Australian humpback dolphin was Caldwell, 1979); and once developed, individual stranded, all recorded whistles showed similar dolphins maintain their signature whistles for long spectral contours, thereby suggesting a signature periods of time.…”

“…Previous studies that have focused on the ers have focused on better understanding how characterization of whistles produced by these members of any given group are able to identify four humpback dolphin species reveal considerindividual conspecifics. First described in bottleable interspecific differences between whistle nose dolphins (Tursiops truncatus) (Lilly, 1963; durations, start and end frequencies, and the over- Caldwell, 1965;Caldwell & Caldwell, 1968), all bandwidths (Zbinden et al, 1977; Parijis & signature whistles are calls with a frequency Corkeron, 2001a;Weir, 2010;Wang et al, 2013; contour unique to an individual; it is the pre- Hoffman et al, 2015). For example, Atlantic dominant call produced when isolated (Caldwell humpback dolphin whistles are of longer duraet al, 1990;Janik & Slater, 1998; tion (by approximately 400 ms) and larger band-2007).…”